(ĭn-vûr'tə-brĭt, -brāt') Adjective Having no backbone or spinal column.

Noun An animal that has no backbone or spinal column and therefore does not belong to the subphylum Vertebrata of the phylum Chordata. Most animals are invertebrates. Corals, insects, worms, jellyfish, starfish, and snails are invertebrates.